Automotive wiring harnesses include low-voltage wiring harnesses and high-voltage wiring harnesses. Conventional fuel vehicles use low-voltage harnesses. The power parts of Electric vehicles (EVs) mainly uses high-voltage harnesses, and the data transmission parts uses low-voltage wiring harnesses. Wiring harnesses are very critical to the driving experience and safety of EVs.
01
Introduction to Automotive harness
Automotive harnesses play the role of connecting, driving and controlling cars, and transmitting data. The main purpose is to transmit power efficiently and with high quality, shield external signal interference and transmit data efficiently and losslessly. The harness is the neural network of the high-voltage system of the EVs and is very important.
Today’s EVs, whether they are Extended-range EVs, Hybrid EVs, Fuel Cell EVs, Hydrogen Engine Vehicles, Pure EVs, or other EVs, require many harnesses. Because of the continuously rising industry application prospects, many leading manufacturers of harnesses have planned. It also attracted many small and medium-sized enterprises to join.
02
Introduction of harness and cables
EVs harness is mainly composed of connectors, terminals, wires, coverings, and other parts. The environment and function of the wire harness affects the cable type, and usually has the characteristics of high temperature resistance, oil resistance, wear resistance, waterproof, anti-corrosion, anti-oxidation, and flame retardant.
Here listed several important cables as below:
– The ambient temperature of the engine and power battery is high, and it generated easily corrosive gas and liquid, so be sure to use high temperature, vibration, friction, and oil-resistant wires;
– The door harness has prime requirements for bending resistance because of the frequent opening and closing of the car door;
– The wire on the automatic transmission must be resistant to high temperature and hydraulic oil, and its temperature stability should be better;
– Use shielded wires for weak signal sensors, such as ABS wheel speed sensors, crankshaft position sensors, etc.;
– Use highly shielded wires for data transmission wires, such as the wires from the 360° camera to the center console;
– The wires on the tailgate should maintain their elasticity at low temperatures, so it should select cold elastic wires to ensure their normal operation.
03
The commonly used wires for wire harnesses
The wires commonly used in automotive wiring harnesses usually use stranded copper wires. Why not use single-strand copper wire?
Here are some points:
– The car wire must be sufficiently likely to withstand the vibration and bending that occur from time to time,
– When electrons flow on the surface of the wire, the use of stranded wire for the same gauge wire can withstand higher current flow.
– Single-strand wires are easy to break into extreme environments, such as long-term vibration and bending in years, and applications in harsh environments with high and low temperatures. Historically, there have been problems and large-scale recalls have occurred.
04
The insulating materials for wire harnesses
The outer quilt commonly used in automobile wiring harnesses is PVC insulating material. The outer quilt insulation material should also have the characteristics of temperature resistance, oil resistance, wear resistance, water resistance, anti-corrosion, anti-oxidation, flame retardant, and so on. At present, the wires used by some car brands mainly include Japanese standard wires and German standard wires. The standard cables used mainly include AV, AVSS, AVSSX, AVX, AEX; the German cables used mainly include FLRY-B, FLR9Y-B.
A gasoline engine powered the traditional car. The traditional car wire is used to transmit control signals, and the current and voltage it bears are tiny. Therefore, the diameter of the wire is small, and the structure is only a conductor plus insulation, which is very simple.
According to the use requirements of HV cables for electric vehicles, HV cables mainly play the role of transmitting energy, and the energy of the battery needs to be transmitted to various subsystems. Therefore, the designed high-voltage wiring harness for electric vehicles must meet the requirements of high voltage and high current transmission.
Electric vehicle high-voltage cables are subject to higher voltages (rated voltage up to 600 V), larger currents (rated current up to 600 A), and strong electromagnetic radiation, so the diameter of the cables increases significantly. In order to prevent electromagnetic radiation from causing strong electromagnetic interference to surrounding electronic equipment and affecting the normal operation of other electronic equipment, it also designed the cable with an anti-electromagnetic interference shielding structure, a coaxial structure. With the combined action of the inner conductor and the outer conductor (shielding), the magnetic field in the cable is distributed in a concentric circle, and the electric field is directed from the inner conductor to the outer conductor, so that the external electromagnetic field around the cable is zero, the electromagnetic field is shielded. Radiation does not interfere with the signal transmission of other cables to ensure the normal operation of electric vehicles.
Because electric vehicle high-voltage cables meet the requirements of high voltage and high current, anti-electromagnetic interference, and also meet the requirements of wear resistance and flame retardant, compared with these materials, silicone rubber has a high breakdown voltage, arc resistance, arc resistance, and flame resistance. Leakage trace resistance, ozone resistance, it also has good high and low-temperature resistance, good insulation performance, stable performance under high temperature and high humidity conditions, flame retardant, etc., silicone rubber comprehensively has good physical and mechanical properties, long service life, price because of its low cost and other advantages, it has become the first choice for high-voltage cable insulation materials for EVs.
05
Shielding materials for wire harnesses
The shielding layer of the cable mainly plays the role of resisting external electromagnetic interference, preventing the electromagnetic field generated by itself from interfering with the surrounding environment and passing fault current during use. Automotive wiring harnesses can be shielded with copper-plastic composite tape wrapping, aluminum-plastic composite tape wrapping shielding, graphene tape, etc. In order to ensure the continuity of the shielding layer and reduce the transfer impedance of the shielding layer, it is usually necessary to place one or more annealed copper wires longitudinally in the shielding layer as a drain wire for copper tape wrapping and aluminum-plastic composite tape wrapping.
Of all the metals in EMI shielding, copper is the most reliable as it works best in reducing electromagnetic and electromagnetic waves. Copper has a higher conductivity, which makes it very effective as an EMI shield. Compared to copper, the conductivity of aluminum is close to 60% of that of copper. According to the quality requirements of automotive wiring harness production standards, aluminum cannot fully meet such strict and demanding requirements. Therefore, the copper-plastic composite tape is the first choice for the shielding material of the automobile wiring harness.
1) The defect of copper-plastic composite tape in terms of high temperature resistance is that it is easy to oxidize. LAMM has specially developed tin-plated copper-plastic composite tape for automobile wiring harnesses. It will not be oxidized under the long-term operating temperature of 120 Celsius.
2)For the door wiring harness with high bending resistance requirements, the Tinned Copper Foil Tape can meet the EMI shielding requirements, but cannot meet the bending resistance requirements. LAMM has specially developed Graphene Tape, the bending times can be over 100,000 times. The shielding effectiveness can be >=120dB in the frequency range of 5MHz～ At present, it is in the testing for the cable samples before bulk goods.
06
Shielding Material Supplier Selection
Because of the strict and demanding requirements of automotive wiring harnesses, and a series of responsibilities such as recall and compensation in the event of a problem, the risks to small and medium-sized shielding tape manufacturers in the supply chain are also relatively high. Therefore, few manufacturers want to join. In addition, good strapping manufacturers can provide high-quality products and services, have experienced engineers, have a deep understanding of automotive wiring harnesses, and have successful application cases of automotive wiring harnesses, which will undoubtedly save the manufacturers a lot of trial-and-error costs.
LAMM is absolutely such a professional manufacturer, serving many Fortune 500 companies. And LAMM also has some successful cases of Japanese EVs Automotive wire harness manufacturers.
